docs: def add_mapped_chain_ids(self, mapped_chains):
          """Add chains by ID into the mapped_chains attribute
  
          Args:
              mapped_chains (str, list): Chain ID or list of IDs
  
          """
          mapped_chains = ssbio.utils.force_list(mapped_chains)
  
          for c in mapped_chains:
              if c not in self.mapped_chains:
                  self.mapped_chains.append(c)
                  log.debug('{}: added to list of mapped chains'.format(c))
              else:
                  log.debug('{}: chain already in list of mapped chains, not adding'.format(c))